Roll-up partition systems protect portals such as windows and doors from break-ins or from wind gusts and flying debris in heavy storms. One type of roll-up partition system is a rolling protective shutter. Rolling protective shutters are conventional and are used to provide protection against extreme weather conditions and to deter theft, for example. Rolling shutters illustratively comprise a plurality of elongate slats that are interconnected by a plurality of hinges. When not in use, the shutter may be retracted into a casing that is usually situated either above or beside the portal, illustratively a window or door. Retracting involves rolling up the shutter onto a roller tube. The shutter is composed of a number of elongated slats that are articulated along their long edges. Forming the shutter out of articulated slats enables the shutter to be retracted compactly yet be strong enough to deter burglary and provide protection against flying debris.
Roll-up partitions in general, and rolling protective shutters in particular, sometimes incorporate one or more torsion spring assemblies to assist in rolling and unrolling the shutters manually or by a powered opening device. In one illustrative arrangement, the assembly is a self-contained modular unit having a spring shaft surrounded by a coiled torsion spring. One end of the spring shaft includes a spring shaft support that is rotatable about the spring shaft, and a spring plate rigidly fixed to the spring shaft and to the proximate end of the torsion spring to prevent rotation of the end of the torsion spring relative to the spring shaft. The other end of the spring shaft includes a spring drive that is rotatable about the spring shaft and rigidly fixed to the other end of the torsion spring. The assembly is inserted into the shutter support member with one end of the spring shaft rigidly fixed to the shutter housing. The spring shaft support and spring drive engage the interior of and rotate with the shutter support member. When the shutter is unrolled, the torsion spring is wound tighter, thereby providing for controlled deployment and providing additional torque to assist in lifting and rolling the shutter onto the shutter support member. During normal operation of the rolling protective shutters, the torsion spring exerts a minimum torque when the shutter is in the rolled position and a maximum torque when the shutter is in the unrolled position.
Taking as an example a shutter for a window opening with a casing located above the window, as the shutter is unrolled the weight of the deployed portion of the shutter tends to cause unrolling to accelerate uncontrollably. To prevent such uncontrolled deployment, with the accompanying noise and potential for injury, the torsion spring biases the roller tube toward the fully retracted position. Rotation of the roller tube about the spring shaft in the direction for deployment tightens the torsion spring, which resists further motion in the direction of rotation, thereby at least partially compensating for the accelerating effect of the ever increasing weight of the unrolled portion of the shutter as it is being deployed. When the roller tube is rotated in the opposite direction to retract the shutter, the bias force of the torsion spring assists the motive force to lift the shutter, and the assistance diminishes as rolling of the shutter onto the roller tube progresses. The degree of bias is determined by the choice of spring and/or any pretensioning there may be when the shutter is fully retracted. The degree of bias, in turn, determines whether a shutter of a predetermined weight will remain deployed or will retract when there is no braking force on the roller tube to prevent rotation. For safety reasons, roller shutters may be equipped with a sufficiently strong torsion spring to fully retract the shutter when there is no braking force applied to the roller tube.
The motive force behind retraction and deployment of the shutter may be provided manually, e.g. by an operator pulling a strap, or electro-mechanically, e.g. by a motor.
Some building code regulations require that manual and electro-mechanical shutters be able to be opened very quickly in the case of an emergency, such as during a fire. A safety mechanism enabling quick release of a roller tube that is engaged to an electric motor is discussed in commonly-assigned U.S. Pat. Nos. 5,975,185 and 6,244,325, the teachings of which are herein incorporated by reference.
In manually operated shutters employing a strap, there is typically a pulley at one end of the roller tube. Illustratively, the pulley is attached to the shutter support member, and the strap is connected between the pulley and a strap recoiler (or “strap box” mounted to one of the shutter tracks or to the wall surrounding the opening. The strap recoiler includes a take-up roll upon which the excess strap is stored and a locking mechanism with a brake tab that locks the strap in place when the strap is pulled tight between the pulley and the strap recoiler. The locking mechanism of the strap recoiler is configured to facilitate retraction and deployment of the strap to roll and unroll the shutter. Illustratively, to roll the shutter to the retracted position, the strap is pulled outwardly away from the shutter track and opening and pulled downwardly toward the strap recoiler. As the strap is pulled outwardly, the locking mechanism releases the strap and allows the force of a torsion spring within the take-up roll to wind the excess strap onto the take-up roll. At the same time, the control strap is unrolled from the pulley, thereby rolling the shutter onto the shutter support member. When the strap is released, the weight of the shutter rotates the pulley and pulls the strap tight between the pulley and the strap recoiler, thereby locking the locking mechanism. To unroll the shutter to the deployed position, the strap is pulled outwardly away from the shutter track and opening and pulled upwardly toward the pulley and shutter housing. As the strap is pulled outwardly, the locking mechanism releases the strap and allows the strap to unwind from the take-up roll. At the same time, the control strap is rolled onto the pulley as the shutter support member rotates due to the weight of the shutter. When the strap is released, the weight of the shutter and the tension in the torsion spring pull the strap tight between the pulley and the strap recoiler, thereby locking the locking mechanism.
To improve the safety of manually operated roller shutters for doors and windows and to meet regulatory objectives, it would be highly desirable to have a quick release mechanism for a manually operated roller shutter employing a strap recoiler.